Study On Purification Of Chlorobenzene Waste Gas From Two-liquid Phase Bioreactors

Chlorobenzenes are concerned as hydrophobic organic contaminants with severe environmental pollution,high biological toxicity and weak biodegradability.Efficient purification of waste gas containing chlorobenzene with fluctuant loading from pharmaceutical and chemical industry has become a difficult issue in the field of waste gas treatment.The conventional biological treatments usually suffer from mass transfer limitations and substrate toxicity,which result in low process elimination capacities and poor stability.Organic/aqueous two-phase bioreactor was established to overcome the disadvantages of traditional biological methods,so as to realize efficient purification for chlorobenzene waste gas.In this study,according to the solvent toxicity,bioavailability to strain LW26 as well as solvent affinity for chlorobenzene,silicone oil was selected as the non-aqueous phase(NAP)of the two-liquid system from octanol,dodecanol,diethylsebacate,silicone oil,hexadecane and octadecene.When silicone oil was added as NAP,strain LW26 could degrade chlorobenzene as high as 33 mg/bottle,whose biodegradation capacity was increased by 50%than the blank.The changes of enzymatic activity with or without silicone oil were investigated.It was suggested that there was no significant difference between the two situation in the lower concentration.While the chlorobenzene concentration reached 22 mg/bottle,the enzymatic activity of strain LW26 without silicone oil subjected to strong inhibition,which results that the enzymatic activity of strain LW26 only is 1/4 of with silicone oil.10%silicon oil was added as organic phase to construct two-phase bioreactor.The influences of inlet concentration,shock loads and stravation on removal efficiency of chlorobenzene in two-phase biotrickling filter(TPBTF)and two-phase stirred tank bioreactor(TPSTB)were examined,respectively.At the same time,the removal efficiency of chlorobenzene in a biotrickling filter(BTF)was compared with the one in a completely mixedstirred tank bioreactor(CSTB).Results revealed that TPSTB achieved removal efficiency more than 90%under the conditions of<1620 mg/m3 inlet concentration of chlorobenzene and EBRT 60s,the removal efficiency only fell to 70.5%at a maximum inlet concentration of 3244 mg/m3.Under the same condition,the removal efficiency of chlorobenzene in the CSTB was as low as 47.6%when the inlet concentration was increased to 3276 mg/m3.Moreover,it has been found that the higher the shock loads,the more obvious the superiority of the effect on the degradation of chlorobenzene in TPSTB than CSTB.TPBTF had a great advantage than BTF on EBRT 90 s,while there was no significant difference between two after the long term running.The maximum elimination capacity in TPBTF was increased by 27.3%than that of BTF in the moderate shock load period.The removal efficiency of the former still can be maintained at about 75%,the latter was only 55%when the loading capacity was up to 205g/m3.h.High throughput sequencing results showed that:the dominant bacteria in TPBTF was increased from 30%at the beginning of the stable period to 55%,which was about twice as much as in BTF.After two weeks of starvation period,the dominant bacteria fell to below 10%in TPBTF,even dropped to about 3%in BTF.